Regulating device

ABSTRACT

A regulating device may include a housing that defines an inlet chamber and an outlet chamber, with a flow restriction seat between the inlet chamber and the outlet chamber. A flow restriction valve is movable relative to the flow restriction seat to adjust the flow between the inlet chamber and the outlet chamber of the regulating device. A servo valve having a servo chamber may be used to adjust the position of the flow restriction valve. The servo chamber may be fluidly coupled to the inlet chamber though a fixed flow restriction and to the outlet chamber though an adjustable flow restriction. A stepper motor may be used to adjust the servo valve to adjust the adjustable flow restriction between the servo chamber and the outlet chamber. This causes a change of the servo pressure, which moves the flow restriction valve and adjusts the flow of the regulating device.

The present application claims priority to European Patent ApplicationNo. 13 190 674.5, filed on Oct. 29, 2013, entitled “REGULATING DEVICE”,which is incorporated herein by reference.

The present patent application relates to a regulating device,preferably to a gas regulating device.

DE 198 21 853 A1 discloses a gas regulating device comprising a housingproviding a gas inlet chamber and a gas outlet chamber. The gasregulating device further comprises gas valves, namely a main gas valve,a safety gas valve and a servo gas valve. The servo gas valve is part ofa servo pressure regulator.

Against this background, the present application provides a regulatingdevice. The regulating device according to the present applicationcomprises at least a housing, a flow restriction valve, a servo valveand a stepper motor. The flow restriction valve and the servo valve arepositioned within the housing. Preferably they are coaxially aligned.The housing provides a first chamber in which a first pressure ispresent and a second chamber in which a second pressure is present. Theflow restriction valve comprises a valve body acting together with aflow restriction seat, wherein the flow restriction valve adjusts theflow from the first chamber into the second chamber. The servo valvecomprises a valve body attached to a membrane, wherein the membranedefines a servo chamber in which a servo pressure is present, whereinthe servo chamber is connected to the first chamber though a fixed flowrestriction element, and wherein the servo chamber is connected to thesecond chamber though an adjustable flow restriction element. Thestepper motor is used for moving the valve body of the servo valvethereby adjusting the adjustable flow restriction element. Theadjustment of the adjustable flow restriction element causes a change ofthe servo pressure present in the servo chamber which is used to movethe flow restriction valve to a position reflecting a defined flowresistance between the valve body of the flow restriction valve (20) andthe flow restriction seat.

The invention makes it possible to regulate the flow restriction valve,which is partly unbalanced because of different pressure levels in thesystem, with a stepper motor. The position of the servo valve may bedirect driven by the stepper motor. The position of the flow restrictionvalve is driven by the pressure within the servo chamber and positionedat a defined position relative to the servo valve. An advantage of adirect driven position of the servo valve by the stepper motor is thatposition and level of flow restriction are precisely defined andcontrolled.

This invention enables defined opening and micro-positioning. Thisinvention rules out overshoot in flow regulation, oscillation and/ornervous behaviour that are typical for pneumatic regulation systems.

This invention enables situation dependent regulation behaviour. Forinstance instabilities during an ignition phase can be filtered orcompletely ignored. Regardless of the position of the servo valve, theflow restriction valve always seeks for equilibrium of axial forces.

When the stepper motor is rotated in a first direction, the valve bodyof the servo valve is moved in a first direction thereby decreasing orclosing the adjustable flow restriction element, thereby changing theservo pressure present in the servo chamber towards the first pressurepresent in the first chamber and thereby increasing or alternativelydecreasing flow resistance over flow restriction valve and therebydecreasing or alternatively increasing flow over the flow restrictionvalve from the first chamber into the second chamber. When the steppermotor is rotated in a second direction, the valve body of the servovalve is moved in a second direction thereby increasing or opening theadjustable flow restriction element, thereby changing the servo pressurepresent in the servo chamber towards the second pressure present in thesecond chamber and thereby decreasing or alternatively increasing flowresistance over flow restriction valve and thereby increasing oralternatively decreasing flow over the flow restriction valve from thefirst chamber into the second chamber. The position of the servo valveis defined as described above by the stepper motor. With the position ofthe servo valve and the equilibrium distance between flow restrictionvalve and servo valve, the position of flow restriction valve and henceflow resistance is precisely defined and controlled.

Preferably, the membrane is positioned between a first membrane supportplate and a second membrane support plate. The valve body of the flowrestriction valve may be coupled to the first membrane support platethrough a hollow valve stem. A servo flow channel provided by the hollowvalve stem, by the valve body of the servo valve and by the firstmembrane support plate, is coupled to the first chamber though the fixedflow restriction element, to the second chamber though the adjustableflow restriction element and to the servo chamber. The fixed flowrestriction element is provided by an opening in the valve body of theflow restriction valve or by an opening in the valve stem. Theadjustable flow restriction element is defined by the valve body of theservo valve and by the first membrane support plate. The valve body ofthe servo valve is moveable relative to the first membrane support platethereby adjusting the adjustable flow restriction element. This designis simple and reliable.

Preferred developments of the invention are provided by the descriptionwhich follows. Exemplary embodiments are explained in more detail on thebasis of the drawing, in which:

FIG. 1 shows a cross sectional view of an illustrative gas regulatingdevice;

FIG. 2 shows a detailed view of part of FIG. 1 in a first state;

FIG. 3 shows the detailed view of FIG. 2 in a second state;

FIG. 4 shows the detailed view of part of FIG. 3; and

FIG. 5 shows a cross sectional view of another illustrative gasregulating device.

FIGS. 1 though 5 show illustrative embodiments of gas regulatingdevices. The use of the invention in connection with gas regulatingdevices is preferred. However, the invention can also be used inconnection with regulating devices for other mediums like water orcooling agents.

FIG. 1 shows a cross sectional view of an illustrative gas regulatingdevice 10. The illustrative gas regulating device 10 comprises a housing11 providing a first chamber 12, hereinafter called first gas chamber,in which a first gas pressure is present, and a second chamber 13,hereinafter called second gas chamber, in which a second gas pressure ispresent. The first chamber 12 can also be called an inlet chamber andthe second chamber 13 can also be called an outlet chamber. The firstgas pressure present in the first gas chamber 12 can also be called aninlet gas pressure and the second gas pressure present in the second gaschamber 13 can also be called an outlet gas pressure.

The illustrative gas regulating device 10 may further comprise a safetyshut-off valve 14 positioned in the housing 10. Other regulating devicesfor other mediums like water or cooling agents may not comprise such asafety shut-off valve 14.

The illustrative safety shut-off valve 14 comprises a valve body 15carried by a valve stem 16. The valve body 15 of the safety shut-offvalve 14 acts together with a valve seat 17 provided by the housing 11.The valve body 15 of the safety shut-off valve 14 is pressed against thevalve seat 17 by a spring element 18 of the safety shut-off valve 14.The valve body 15 of the safety shut-off valve 14 can be lifted up fromthe valve seat 17 against the force of the spring element 18 by anactuator 19, namely by energizing a magnetic coil.

A gas flow from the first gas chamber 12 into the second gas chamber 13is impossible when the valve body 15 of the safety shut-off valve 14 ispressed against the valve seat 17 provided by the housing 11. A gas flowfrom the first gas chamber 12 into the second gas chamber 13 is possiblewhen the valve body 15 of the safety shut-off valve 14 is lifted up fromthe valve seat 17 provided by the housing 11.

The gas regulating device 10 further comprises a flow restriction valve20 positioned in the housing 11. The flow restriction valve 20 comprisesa valve body 21 acting together with a flow restriction seat 22 providedby the housing 11. It is also possible that the flow restriction seat 22is not provided by the housing 11 but by a different part placed insidethe housing 11. The flow restriction valve 20 adjusts the gas flow fromthe first gas chamber 12 into the second gas chamber 13 when the valvebody 15 of the safety shut-off valve 14 is lifted up from the valve seat17 provided by the housing 11.

FIGS. 1 and 2 show the flow restriction valve 20 in a relatively closedstate and FIG. 3 shows the flow restriction valve 20 in a relativelyopened state. In both states, the flow restriction valve 20 allows a gasflow from the first gas chamber 12 into the second gas chamber 13,namely in the state of FIGS. 1 and 2 a relatively small or relativelylow gas flow and in the state of FIG. 3 a relatively big or relativelyhigh gas flow.

The illustrative flow restriction valve 20 is shown coaxially aligned tothe safety shut-off valve 14. Coaxial alignment of flow restrictionvalve 20 and safety shut-off valve 14 is optional. The invention wouldalso work when the same are eccentric placed or when the flowrestriction valve 20 is placed at an angle in respect to the shut-offvalve 14.

The illustrative gas regulating device 10 further comprises a servovalve 23 positioned in the housing 11. The servo valve 23 comprises avalve body 24 attached to a membrane 25. The membrane 25 defines a servogas chamber 26 in which a servo gas pressure is present. The servo gaschamber 26 is connected to the first (inlet) gas chamber 12 though afixed flow restriction element, hereinafter called fixed orifice 27. Theservo gas chamber 26 is also connected to the second (outlet) gaschamber 13 though an adjustable flow restriction element, hereinaftercalled adjustable orifice 28.

The illustrative membrane 25 is positioned between a first, uppermembrane support plate 29 and a second, lower membrane support plate 30.The illustrative servo valve 23 including the valve body 24, themembrane 25 and the membrane support plates 29, 30 is shown positionedin a space defined by a lower housing section, wherein the membrane 25divides that space, with the servo gas chamber 26 positioned below themembrane 25 and a gas chamber 36 positioned above the membrane 25.

The gas chamber 36 positioned above the membrane 25 is shown connectedwith the second gas chamber 13 by an opening 37 in the housing 11 sothat the same gas pressure is present within the gas chamber 36positioned above the membrane 25 and the second gas chamber 13.

The illustrative valve body 21 of the flow restriction valve 20 ismechanically coupled to the first membrane support plate 29 through ahollow valve stem 31. In some instances, valve stem 31 and firstmembrane support plate 29 can be provided by one single part. In theembodiment shown, a servo gas flow channel 32 is provided by the hollowvalve stem 31, by the valve body 24 of the servo valve 23 and by thefirst membrane support plate 29. The servo gas flow channel 32 iscoupled to the first gas chamber 12 through the fixed orifice 27, iscoupled to the second gas chamber 13 through the adjustable orifice 28,and is coupled to the servo gas chamber 26. The servo gas chamber 26 isconnected to the servo gas flow channel 32 between the fixed orifice 27and the adjustable orifice 28. FIG. 4 illustrates the servo gas flow 38though the servo gas flow channel 32 between the chambers 12, 13, 26.The area above the membrane 25 around the servo valve 23 is connectedwith the servo pressure, which occurs between the fixed orifice 27 andadjustable orifice 28.

The fixed orifice 27 is provided by an opening in the valve body 21 ofthe flow restriction valve 20. Alternatively, the fixed orifice 27 isprovided by an opening in the valve stem 31. In the embodiment shown,the adjustable orifice 28 is provided by the valve body 24 of the servovalve 23 and by the first membrane support plate 29. The servo valve 23is shown coaxially aligned to safety shut-off valve 14 and to the flowrestriction valve 20, but this is not required.

The illustrative gas regulating device 10 further comprises a gas tightstepper motor 33 for moving the valve body 24 of the servo valve 23thereby adjusting the adjustable orifice 28. The stepper motor 33 actstogether with a spindle 34 and a threaded section of the valve body 24of the servo valve 23. By rotating the stepper motor 33 the spindle 34becomes rotated, whereby an outer thread of the spindle 34 engages withan inner thread of the threaded section of the valve body 24 therebycausing a linear movement of the valve body 24 of the servo valve 23.

In this case, the membrane 25 prevents the servo valve 23 for rotatingwith the spindle 34. It is also possible to use other means like a pin,to prevent the servo valve 23 from rotating with the spindle 34. Thespindle 34 converts the rotation of the stepper motor 33 into a linearmovement of the valve body 24 of the servo valve 23. So, in theillustrative embodiment, the valve body 24 of the servo valve 23 ismoveable relative to the first membrane support plate 29 by the steppermotor 33 thereby adjusting the adjustable orifice 28.

A spring element 35 acts on the valve body 24 of the servo valve 23.This spring element 35 is optional, to push any axial play in thestepper motor 33, or between the spindle 34 and the threaded section ofthe valve body 24 to one side. The spring element 35 does not have asupporting function towards linear movement of the valve body 24 of theservo valve 23.

Regardless of the position of the servo valve 23, the flow restrictionvalve 20 always seeks for equilibrium of axial forces. In FIG. 2 theaxial forces F1, F2, F3 and F4 acting on the pressure regulation valve20 and on the servo valve 23 are shown, whereby the axial forces F1, F2,F3 and F4 depend on the pressure p1 within the first gas chamber 12, thepressure p2 within the second gas chamber 13 and the servo gas pressurep3 within the servo gas chamber as follows:

F1=p1*A1

F2=p2*A2

F3=p2*A3

F4=P3*A4

wherein A1, A2 are the effective areas of the valve body 21, and whereinA3, A4 are the effective areas of the support plates 29, 30 and membrane25. A1 might be equal to A2 and A3 might be equal to A4.

Assuming that an additional undefined force F5 is acting on the flowrestriction valve 20, in a static situation the following scenarios arepossible:

-   -   (1) The resulting force FR=F1−F2+F3−F4+F5>0: Then the flow        restriction valve 20 is pushed downwards towards the servo valve        23 which has a defined position which is fixed by the spindle 34        for the moment. Result of this movement is the opening of that        adjustable orifice 28 decreases and the flow resistance        increases through adjustable orifice 28. Because of this        increased flow resistance, servo pressure p3 will increase        towards pressure p1, and force F4 will increase accordingly.        Resulting force FR will decrease towards zero.    -   (2) The resulting force FR=F1−F2+F3−F4+F5<0: Then the flow        restriction valve 20 is pushed upwards away from the servo valve        23 which has a defined position. Result of this movement is that        opening of the adjustable orifice 28 increases and the flow        resistance decreases through the adjustable orifice 28. Because        of this decreased flow resistance, servo pressure p3 will        decrease towards pressure p2 and force F4 will decrease        accordingly. Resulting force FR will increase towards zero.

If resulting force FR is not equal to zero, the servo pressure p3 willchange to compensate for any unbalance.

In a dynamic situation, the following scenarios are possible:

-   -   (1) When the stepper motor 33 is rotated in a first direction,        the valve body 24 of the servo valve 23 is moved in a first        direction towards the flow restriction valve 20: thereby        decreasing or closing the adjustable orifice 28; thereby        changing the servo gas pressure present in the servo gas chamber        26 towards the first gas pressure present in the first gas        chamber 12; thereby creating a resulting force that acts on the        membrane 25 and flow restriction valve 20 in the same direction        as the moving direction of the servo valve 23; thereby moving        the flow restriction valve 20 in the same direction as the moved        servo valve 23, away from the servo valve 23; thereby restoring        increasing or opening the adjustable orifice 28; thereby        restoring servo pressure p3; thereby restoring equilibrium of        forces; thereby increasing the flow resistance over flow        restriction valve 20; and thereby decreasing the gas flow over        the flow restriction valve 20 from the first gas chamber 12 into        the second gas chamber 13. With such an actuation, the gas        regulating device 10 can be transferred from the state shown in        FIG. 3 into the state shown in FIGS. 1 and 2.    -   (2) When the stepper motor 33 is rotated in a second direction,        the valve body 24 of the servo valve 22 is moved in a second        direction opposite to the above first direction: thereby        increasing or opening the adjustable orifice 28; thereby        changing the servo gas pressure present in the servo gas chamber        26 towards the second gas pressure present in the second gas        chamber 13; thereby creating a resulting force that acts on the        membrane 25 and flow restriction valve 20 in the opposite        direction as the moving direction of the servo valve 23; thereby        moving the flow restriction valve 20 in the opposite direction        as the moved servo valve 23; thereby restoring decreasing or        closing the adjustable orifice 28; thereby restoring servo        pressure p3; thereby restoring equilibrium of forces; thereby        decreasing flow resistance over flow restriction valve 20; and        thereby increasing gas flow over the flow restriction valve 20        from the first gas chamber 12 into the second gas chamber 13.        With such an actuation, the gas regulating device 10 can be        transferred from the state shown in FIGS. 1 and 2 into the state        shown in FIG. 3.

The above actuations are initiated by rotating the stepper motor 33 andthereby moving the valve body 24 of the servo valve 23. The movements ofthe valve body 24 of the servo valve 23 cause a pressure change withinthe servo gas chamber 26. This pressure change within the servo gaschamber 26 finally causes the movement of the valve body 21 of the flowrestriction valve 20, and thereby changes the gas flow over the flowrestriction valve 20 from the first gas chamber 12 into the second gaschamber 13. The position of the flow restriction valve 20 depends on theposition of the servo gas valve 23.

The adjustment of the position of the valve body 21 of the flowrestriction valve 20 and thereby the adjustment of the flow resistanceover the flow restriction valve 20 takes place until the system is inequilibrium. In equilibrium, the flow restriction valve 20 is in forceequilibrium and flow equilibrium, meaning that resultant forces that acton the restriction valve 20 are zero and that the servo flow 23 thatexits the servo chamber 26 via the adjustable orifice 28 equals theservo flow that enters the servo chamber 26 via the fixed orifice 27.Servo flow that exits the servo chamber 26 via the adjustable orifice 28defines the distance between the servo valve 23 and the upper supportplate 29 precisely.

The illustrative gas regulating device 10 comprises the flow restrictionvalve 20 positioned inside, above or below a flow port of safetyshut-off valve 14. The illustrative gas regulating device 10 providesthree levels of pressure, namely first/inlet gas pressure, second/outletgas pressure and servo gas pressure. The first/inlet gas pressure isinput from the system. The second/outlet gas pressure is the result ofthe position of the flow restriction valve 20.

Inside the flow restriction valve 20 is the servo gas valve 23positioned such that it can manipulate the servo gas pressure level byopening or closing the adjustable outlet orifice 28 to make use of thatservo gas pressure for moving or positioning the flow restriction valve20 at a defined distance from that servo gas valve 23. The position ofthat servo gas valve 23 is defined by the stepper motor 23. With theposition of the servo gas valve 23 and the defined distance between flowrestriction valve 20 and servo gas valve 23, the position flowrestriction valve 20 and hence flow resistance over the flow restrictionvalve 20 is precisely defined and controlled.

In some cases, the second gas pressure present within the second gaschamber 13 can be measured by a sensor (not shown). In this case, thestepper motor 33 may be operated on basis on the pressure measured bysaid sensor in such a way that the second gas pressure within the secondgas chamber 13 is kept constant at a defined level.

In this case, the flow restriction valve 20 is used as a pressurecontroller. Alternatively, it is also possible to measure the gas flowthrough the gas regulating device and to operate stepper motor 33 tokeep the gas flow constant. In this case, the flow restriction valve 20is used as a flow controller.

In the illustrative embodiment shown in FIGS. 1 to 4, the flowrestriction valve 20 and the safety shut-off valve 14 become opened inopposite directions. In FIGS. 1 to 4, the safety shut-off valve 14 ismoved upwards to become opened and flow restriction valve 20 is moveddownwards to become opened. So, in FIGS. 1 to 4, the flow restrictionvalve 20 opens in the direction of the gas flow through the valve set 17when the safety shut-off valve 14 is opened.

FIG. 5 shows an illustrative embodiment of a gas regulating device 10 inwhich the flow restriction valve 20 and the safety shut-off valve 14become opened in the same direction. In FIG. 5, the safety shut-offvalve 14 and the flow restriction valve 20 are both moved upwards tobecome opened. So, in FIG. 5 the flow restriction valve 20 opens in theopposite direction of the gas flow through the valve set 17 when thesafety shut-off valve 14 is opened.

In this case the following applies: When the stepper motor is rotated ina first direction, the valve body of the servo valve is moved in a firstdirection thereby decreasing or closing the adjustable flow restrictionelement, thereby changing the servo pressure present in the servochamber towards the first pressure present in the first chamber andthereby decreasing flow resistance over flow restriction valve andthereby increasing flow over the flow restriction valve from the firstchamber into the second chamber. When the stepper motor is rotated in asecond direction, the valve body of the servo valve is moved in a seconddirection thereby increasing or opening the adjustable flow restrictionelement, thereby changing the servo pressure present in the servochamber towards the second pressure present in the second chamber andthereby increasing flow resistance over flow restriction valve andthereby decreasing flow over the flow restriction valve from the firstchamber into the second chamber. The position of the servo valve isdefined as described above by the stepper motor. With the position ofthe servo valve and the equilibrium distance between flow restrictionvalve and servo valve, the position of flow restriction valve and henceflow resistance is precisely defined and controlled. All other detailsare the same. For that, identical reference signs are used and referenceis made to the description of FIGS. 1 to 4.

LIST OF REFERENCE SIGNS

-   10 gas regulating device-   11 housing-   12 first/inlet gas chamber-   13 second/outlet gas chamber-   14 safety shut-off valve-   15 valve body-   16 valve stem-   17 valve seat-   18 spring element-   19 actuator-   20 flow restriction valve-   20 valve body-   21 flow restriction seat-   22 servo valve-   23 valve body-   25 membrane-   26 servo gas chamber-   27 fixed orifice-   28 adjustable orifice-   29 first, upper membrane support plate-   30 second, lower membrane support plate-   31 valve stem-   32 servo gas flow channel-   33 stepper motor-   34 spindle-   35 spring element-   36 gas chamber-   37 opening-   38 gas flow

What is claimed is:
 1. A regulating device, comprising a housingproviding a first chamber in which a first pressure is present and asecond chamber in which a second pressure is present; a flow restrictionvalve positioned in the housing, wherein the flow restriction valvecomprises a valve body acting together with a flow restriction seat, andwherein the flow restriction valve adjusts the flow from the firstchamber into the second chamber; a servo valve positioned in thehousing, wherein the servo valve comprises a valve body attached to amembrane, wherein the membrane defines at least part of a servo chamberin which a servo pressure is present, wherein the servo chamber isconnected to the first chamber though a fixed flow restriction element,and the servo chamber is connected to the second chamber though anadjustable flow restriction element; and a stepper motor for moving thevalve body of the servo valve, thereby adjusting the adjustable flowrestriction element, wherein the adjustment of the adjustable flowrestriction element causes a change of the servo pressure present in theservo chamber which is used to move the flow restriction valve to aposition reflecting a defined flow resistance between the valve body ofthe flow restriction valve and the flow restriction seat.
 2. Theregulating device of claim 1, wherein: when the stepper motor is drivenin a first direction, the valve body of the servo valve is moved in afirst direction thereby decreasing or closing the adjustable flowrestriction element, thereby changing the servo pressure present in theservo chamber towards the first pressure present in the first chamberand thereby increasing or alternatively decreasing flow resistance overflow restriction valve and thereby decreasing or alternativelyincreasing flow over the flow restriction valve from the first chamberinto the second chamber; when the stepper motor is driven in a seconddirection, the valve body of the servo valve is moved in a seconddirection thereby increasing or opening the adjustable flow restrictionelement, thereby changing the servo pressure present in the servochamber towards the second pressure present in the second chamber andthereby decreasing or alternatively increasing flow resistance over flowrestriction valve and thereby increasing or alternatively decreasingflow over the flow restriction valve from the first chamber into thesecond chamber.
 3. The regulating device of claim 1, wherein: themembrane is positioned between a first membrane support plate and asecond membrane support plate; the valve body of the flow restrictionvalve is coupled to the first membrane support plate through a hollowvalve stem; a servo flow channel provided by the hollow valve stem, bythe valve body of the servo valve and by the first membrane supportplate, is coupled to the first chamber though the fixed flow restrictionelement, to the second chamber though the adjustable flow restrictionelement, and to the servo chamber; the fixed flow restriction element isprovided by an opening in the valve body of the flow restriction valveor by an opening in the valve stem; the adjustable flow restrictionelement is defined by the valve body of the servo valve and by the firstmembrane support plate.
 4. The regulating device of claim 3, wherein theservo chamber is connected to the servo flow channel between the fixedflow restriction element and the adjustable flow restriction element. 5.The regulating device of claim 3, wherein the valve body of the servovalve is moveable relative to the first membrane support plate by thestepper motor to thereby adjust the adjustable flow restriction element.6. The regulating device of claim 1, wherein the valve body of the servovalve is coupled to the stepper motor by a spindle, wherein the spindleconverts a rotation of the stepper motor into a linear movement of thevalve body of the servo valve.
 7. The regulating device of claim 1,wherein the second pressure within the second chamber is measured by asensor, and that the stepper motor is operated on basis on the pressuremeasured by the sensor in such a way that the second pressure within thesecond chamber is kept substantially constant.
 8. The regulating deviceof claim 1, wherein the flow restriction valve and the servo valve arecoaxially aligned.
 9. The regulating device of claim 1, furthercomprising a safety shut-off valve positioned in the housing, whereinthe safety shut-off valve comprises a valve body acting together with avalve seat provided by the housing, wherein a flow from the firstchamber into the second chamber is prevented when the valve body of thesafety shut-off valve is pressed against the valve seat provided by thehousing, wherein a flow from the first chamber into the second chamberis possible when the valve body of the safety shut-off valve is liftedup from the valve seat provided by the housing.
 10. The regulatingdevice of claim 9, wherein the safety shut-off valve, the flowrestriction valve and the servo valve are all coaxially aligned.
 11. Theregulating device of claim 9, wherein the flow restriction valve adjuststhe gas flow from the first chamber into the second chamber when thevalve body of the safety shut-off valve is lifted up from the valve seatprovided by the housing.
 12. The regulating device of claim 1, whereinthe regulating device is a gas regulating device.
 13. A gas regulatingdevice, comprising a housing defining a gas inlet chamber having an gasinlet pressure and a gas outlet chamber having a gas outlet pressure,the housing further defining a flow restriction seat between the gasinlet chamber and the gas outlet chamber; a flow restriction valvemovable relative to the flow restriction seat of the housing to adjust aflow between the gas inlet chamber and the gas outlet chamber; a servovalve having a servo chamber in which a servo pressure is present,wherein the servo chamber is fluidly coupled to the gas inlet chamberthough a fixed flow restriction and to the gas outlet chamber though anadjustable flow restriction; and a stepper motor for adjusting theadjustable flow restriction between the servo chamber and the gas outletchamber, which is configured to cause a change of the servo pressurepresent in the servo chamber, which is configured to move the flowrestriction valve relative to the flow restriction seat to therebyadjust the flow between the gas inlet chamber and the gas outlet chamberof the housing.
 14. The gas regulating device of claim 13, wherein theservo valve comprises a membrane, wherein the membrane defines at leastpart of the servo chamber in which the servo pressure is present. 15.The gas regulating device of claim 14, wherein: when the stepper motoris driven in a first direction, the servo valve is moved in a firstdirection thereby decreasing or closing the adjustable flow restriction,thereby changing the servo pressure present in the servo chamber towardsthe gas inlet pressure present in the gas inlet chamber and therebydecreasing or alternatively increasing flow between the gas inletchamber and the gas outlet chamber; and when the stepper motor is drivenin a second direction, the servo valve is moved in a second directionthereby increasing or opening the adjustable flow restriction, therebychanging the servo pressure present in the servo chamber towards the gasoutlet pressure present in the gas outlet chamber and thereby increasingor alternatively decreasing flow between the gas inlet chamber and thegas outlet chamber.
 16. The gas regulating device of claim 15, wherein:the membrane is positioned between a first membrane support plate and asecond membrane support plate; the flow restriction valve is coupled tothe first membrane support plate through a hollow valve stem; and aservo flow channel provided by the hollow valve stem of the flowrestriction valve, by a valve body of the servo valve and by the firstmembrane support plate, is coupled to the gas inlet chamber though thefixed flow restriction, to the gas outlet chamber though the adjustableflow restriction, and to the servo chamber.
 17. The gas regulatingdevice of claim 16, wherein: the fixed flow restriction is provided byan opening in the flow restriction valve; and the adjustable flowrestriction is defined between the valve body of the servo valve and bythe first membrane support plate.
 18. A method for adjusting a positionof a flow restriction valve between a gas inlet chamber and a gas outletchamber in order to adjust the flow of gas between the gas inlet chamberand a gas outlet chamber, the method comprising: using a stepper motorto adjust a position of a servo valve in a first direction, whichdecreases a size of an adjustable flow restriction between a servochamber and the gas outlet chamber, wherein a fixed flow restriction ispresent between the servo chamber and the gas inlet chamber, whereindecreasing the size of the adjustable flow restriction changes apressure in the servo chamber towards a gas inlet pressure in the gasinlet chamber and moves the flow restriction valve in a first directionthereby adjusting the flow of gas between the gas inlet chamber and thegas outlet chamber; and using the stepper motor to adjust the positionof the servo valve in a second direction, which increases the size ofthe adjustable flow restriction between the servo chamber and the gasoutlet chamber, wherein increasing the size of the adjustable flowrestriction changes the pressure in the servo chamber towards a gasoutlet pressure in the gas outlet chamber and moves the flow restrictionvalve in a second direction thereby adjusting the flow of gas betweenthe gas inlet chamber and the gas outlet chamber.
 19. The method ofclaim 18, wherein decreasing the size of the adjustable flow restrictionchanges the pressure in the servo chamber towards the gas inlet pressurein the gas inlet chamber and decreases the flow of gas between the gasinlet chamber and a gas outlet chamber.
 20. The method of claim 19,wherein increasing the size of the adjustable flow restriction changesthe pressure in the servo chamber towards the gas outlet pressure in thegas outlet chamber and increases the flow of gas between the gas inletchamber and a gas outlet chamber.